Photopolymerizable composition, photopolymerizable ink jet ink, ink cartridge, and coated matter

ABSTRACT

A photopolymerizable composition includes diethyleneglycol dimethacrylate and methacrylic acid ester having a phosphoric group.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is based on and claims priority pursuant to 35U.S.C. §119 to Japanese Patent Applications Nos. 2013-091979 and2014-035223, filed on Apr. 25, 2013 and Feb. 26, 2014, respectively inthe Japan Patent Office, the entire disclosure of which is herebyincorporated by reference herein.

BACKGROUND

1. Technical Field

The present invention relates to a photopolymerizable composition, and aphotopolymerizable inkjet ink, an ink cartridge containing the ink and acoated matter coated therewith.

2. Description of the Related Art

PCT Japanese published national phase application No. 2004-526820discloses a photopolymerizable composition and a photopolymerizableinkjet ink using (meth)acrylic acid ester.

However, many of monomers used in conventional photopolymerizable inkjetinks have toxicities. Particularly, inexpensive and easily-obtainable(meth)acrylic acid esters occasionally cause allergies when contactingskins.

The present inventors have found some (meth)acrylic acid esters and(meth)acryl amides having no problem of skin sensitization. As disclosedin Japanese published unexamined application No. JP-2012-140593-A, theynoticed that methacrylate is less toxic than acrylate and suggested aninkjet ink mainly using methacrylate.

The inkjet ink is required to have low viscosity even when includingvarious materials such as a pigment and an additive so as not to preventthe ink from ejecting. Water can be included therein to lower theviscosity and the photopolymerizable inkjet ink including water isknown. However, since penetration drying cannot be expected fromnon-permeable substrates as mentioned later, a process of vaporizingwater is needed for higher printing speed and efficiency, resulting inenlargement of the apparatus.

When the photopolymerizable composition is used for brush coating, anorganic solvent can be used. Since the organic solvent is volatilizedand discharged in the atmosphere, the organic solvent is preferably usedin a minimum amount in consideration of influence on the environment. Onthe other hand, when used as an inkjet ink, the organic solvent havinghigh volatility occasionally increases viscosity of the ink, resultingin poor rejection thereof. The organic solvent needs adjustment involatility for the ink to stably eject.

SUMMARY

Accordingly, one object of the present invention is to provide aphotopolymerizable composition having no problem of skin sensitizationand improved adherence to metal surfaces.

Another object of the present invention is to provide aphotopolymerizable inkjet ink using the photopolymerizable composition.

A further object of the present invention is to provide an ink cartridgecontaining the inkjet ink.

Another object of the present invention is to provide a coated matterusing the photopolymerizable composition.

These objects and other objects of the present invention, eitherindividually or collectively, have been satisfied by the discovery of aphotopolymerizable composition including diethyleneglycol dimethacrylateand methacrylic acid ester having a phosphoric group.

These and other objects, features and advantages of the presentinvention will become apparent upon consideration of the followingdescription of the preferred embodiments of the present invention takenin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Various other objects, features and attendant advantages of the presentinvention will be more fully appreciated as the same becomes betterunderstood from the detailed description when considered in connectionwith the accompanying drawings in which like reference charactersdesignate like corresponding parts throughout and wherein:

FIG. 1 is a schematic view illustrating an example of an ink bag of theink cartridge of the present invention; and

FIG. 2 is a schematic view illustrating an example of the ink cartridgeof the present invention housing the ink bag.

DETAILED DESCRIPTION

In some cases, on a chassis or a molded product, a metallic layer suchas aluminum and stainless is formed to impart metallic gloss thereto forthe purpose of improving design. However, conventionalphotopolymerizable compositions are difficult to adhere to the surfaceof a metal to prevent the surface from eroding or protect the surface.

Because of these reasons, a need exists for a photopolymerizablecomposition and a photopolymerizable inkjet ink having no problem ofskin sensitization and improved adherence to metal surfaces.

The present invention provides a photopolymerizable composition (an ink)having no problem of skin sensitization and improved adherence to metalsurfaces.

More particularly, the present invention relates to a photopolymerizablecomposition including diethyleneglycol dimethacrylate and methacrylicacid ester having a phosphoric group.

Further, the present inventors found a photopolymerizable compositionincluding caprolactone-modified dipentaerythritol hexaacrylate and/orethyleneoxide-modified trimethylolpropane trimethacrylate as wellimproves in strength of a coating film formed therewith.

The ethyleneoxide-modified trimethylol propane trimethacrylate has aformula [CH₃CH₂C—{CH₂(O—CH₂CH₂)_(x)—OCOC(CH₃)═CH₂}₃]. X represents alength of ethyleneoxide part. The larger the X, the larger the molecularweight and the higher the viscosity. The higher the viscosity, the moredifficult to use as an inkjet ink material. However, monomers of a4 toa8 are expected to improve processing suitability. It is preferable notto use trimethylol propane trimethacrylate (x=0) because of having asymbol mark “N” representing environmental dangerous hazardousness and arisk phrase “R51/53” representing acute aquatic toxicity and long-termadverse affect in EU. Directive 67/548/EEC in consideration of influenceon the environment.

X of the ethyleneoxide-modified trimethylol propane trimethacrylate usedin Examples is 1. The ethyleneoxide-modified trimethylol propanetrimethacrylate does not have a problem of viscosity as a materialincluded in an inkjet ink. The photopolymerizable composition includingthis forms a coating film having sufficient strength. Further, theethyleneoxide-modified trimethylol propane trimethacrylate has noproblem of skin sensitization, environmental dangerous hazardousness,acute aquatic toxicity and long-term adverse affect.

The photopolymerizable composition negative for skin sensitizationrefers to a compound satisfying at least the following (1) or (2):

-   (1) a compound having a Stimulation Index (SI value) of less than 3,    where the Stimulation Index indicates the level of sensitization as    measured by a skin sensitization test based on the LLNA (Local Lymph    Node Assay); and-   (2) a compound evaluated as “negative for skin sensitization” or “no    skin sensitization” in its MSDS (Material Safety Data Sheet).

Regarding the above (1), the compound having the SI value of less than 3is considered as negative for skin sensitization as described inliteratures, for example, “Functional Material” (Kino Zairyou) 2005,September, Vol. 25, No. 9, p. 55. The lower SI value means the lowerlevel of skin sensitization. Thus, in the present invention, a monomerhaving the lower SI value is preferably used. The SI value of themonomer used is preferably less than 3, more preferably 2 or lower, andeven more preferably 1.6 or lower.

However, those affirmatively applied to human bodies as medicalapplications can be assumed to have no particular problem.

Diethyleneglycol dimethacrylate is suitably used as a material of thephotopolymerizable composition usable as an inkjet ink because of havingno problem of skin sensitization and low viscosity. However, thediethyleneglycol dimethacrylate does not have sufficient interactionwith metal surfaces and the photopolymerizable composition is difficultto have adherence thereto. However, including the methacrylic acid esterhaving a phosphoric group, the photopolymerizable composition hasadherence to metal surfaces such as aluminum and stainless. Thephotopolymerizable composition including the methacrylic acid esterhaving a phosphoric group, having a formula(CH₂═C(CH₃)COOCH₂CH₂O)₂—P(═O)OH has sufficient low viscosity andproduces a coating film having sufficient strength.

The photopolymerizable composition preferably includes thediethyleneglycol dimethacrylate in an amount of from 45 to 80 parts byweight per 100 parts by weight of monomer components.

The methacrylic acid ester having a phosphoric group generates a stronginteraction with a polarity of the phosphoric group and has a viscosityhigher than that of typical methacrylic acid ester. Thephotopolymerizable composition preferably includes the methacrylic acidester having a phosphoric group in an amount of from 5 to 30 parts byweight per 100 parts by weight of monomer components because of havingsuitable viscosity when used as an inkjet ink. The skin sensitization ofthe methacrylic acid ester having a phosphoric group is not evaluated,but as “Dental Material. Machine 5(1)144-154(1986)” shows, it isconsidered as a dental material and has no particular problem againsthuman bodies.

Further, the photopolymerizable composition of the present inventionpreferably includes caprolactone-modified dipentaerythritol hexaacrylateand ethyleneoxide-modified trimethylolpropane trimethacrylate aspolymerizable monomers. The photopolymerizable composition preferablyincludes the caprolactone-modified dipentaerythritol hexaacrylate in anamount of form 3 to 15 parts by weight, and more preferably from 5 to 10parts by weight; the ethyleneoxide-modified trimethylolpropanetrimethacrylate in an amount of form 15 to 60 parts by weight, and morepreferably from 20 to 50 parts by weight per 100 parts by weight ofmonomer components, respectively.

When the photopolymerizable composition is used as an inkjet ink, theink preferably has properties meeting with required specifications of aninkjet ejection head used. Various ejection heads are marketed from manymanufacturers, and some of them have large ejection power to eject anink having high viscosity and wide thermostat. The ink preferably has aviscosity of from 2 to 150 mPa·s, and more preferably from 5 to 18 mPa·sat 25° C. However, the thermostat of the ejection head can be used. Whenthe viscosity is too high at 25° C., the head may be heated whennecessary to make the ink have lower viscosity. When heated at from 45to 60° C., the ink preferably has a viscosity of from 5 to 18 mPa·sthereat.

The following (meth)acrylates and (meth)acryl amides can be usedtogether as long as a resulting ink does not have a problem, even thoughthey have a problem of skin sensitization in some degrees when usedalone, or skin sensitization thereof is not confirmed.

Specific examples thereof include, but are not limited to, ethyleneglycol di(meth)acrylate, hydroxypivalic acid neopentyl glycoldi(meth)acrylate, γ-butyrolactone acrylate, isobornyl(meth)acrylate,formulated trimethylol propane mono(meth)acrylate, polytetramethyleneglycol di(meth)acrylate, trimethylol propane (meth)acrylic acidbenzoate, diethyleneglycol diacrylate, triethylene glycol diacrylate,tetraethylene glycol diacrylate, polyethylene glycol diacrylate[CH₂═CH—CO(OC₂H₄)_(n)—OCOCH═CH₂(n≈9)], [CH₂═CH—CO(OC₂H₄)_(n)—OCOCH═CH₂(n≈14)], [CH₂═CH—CO(OC₂H₄)_(n)—OCOCH═CH₂(n≈23)], dipropylene glycoldi(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropyleneglycol dimethacrylate [CH₂═C(CH₃)—CO—(OC₃H₆)_(n)—OCOC(CH₃)═CH₂(n≈7)],1,3-butanediol diacrylate, 1,4-butanediol di(meth)acrylate,1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate,neopentyl glycol di(meth)acrylate, tricyclodecane dimethanol diacrylate,propylene oxide-modified bisphenol A di(meth)acrylate, polyethyleneglycol di(meth)acrylate, dipentaerythritol hexa(meth)acrylate,(meth)acryloyl morpholine, 2-hydroxypropyl (meth)acryl amide, propyleneoxide-modified tetramethylol methane tetra(meth)acrylate,dipentaerythritol hydroxypenta(meth)acrylate, caprolactone-modifieddipentaerythritol hydroxypenta(meth)acrylate, ditrimethylol propanetetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, trimethylolpropane acrylate, ethylene oxide-modified trimethylol propanetriacrylate, propylene oxide-modified trimethylol propanetri(meth)acrylate, caprolactone-modified trimethylol propanetri(meth)acrylate, pentaerythritol tri(meth)acrylate,tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, ethoxylatedneopentyl glycol di(meth)acrylate, propylene oxide-modified neopentylglycol di(meth)acrylate, propylene oxide-modified glyceryltri(meth)acrylate, polyester di(meth)acrylate, polyestertri(meth)acrylate, polyester tetra(meth)acrylate, polyesterpenta(meth)acrylate, polyester poly(meth)acrylate, N-vinyl caprolactam,N-vinyl pyrrolidone, N-vinyl formamide, polyurethane di(meth)acrylate,polyurethane tri(meth)acrylate, polyurethane tetra(meth)acrylate,polyurethane penta(meth)acrylate and polyurethane poly(meth)acrylate.

When using a quite high energy light source, such as electron beams, αrays, β rays, γ rays or X rays, polymerization reaction can proceedwithout polymerization initiator. Since this is a conventionally knownmatter, the equipment is very expensive and the maintenance iscomplicated, this not described in detail in the present invention.

The photoradical polymerization initiators include, but are not limitedto, a self-cleaving photopolymerization initiator and ahydrogen-abstracting polymerization initiator. These may be used alone,or in combination. Specific examples of the self-cleavingphotopolymerization initiator include, but are not limited to,1-hydroxy-cyclohexyl-phenyl-ketone,2-hydroxy-2-methyl-1-phenylpropan-1-one,1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one,2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl}-2-methyl-1-propan-1-one,phenylglyoxylic acid methyl ester,2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one,2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone-1,2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-yl-phenyl)butan-1-one,bis(2,4,6-trimethylbenzoyl)phenyl phosphine oxide,bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide,2,4,6-trimethylbenzoylphosphine oxide,1,2-octanedion-[4-(phenylthio)-2-(o-benzoyloxime)],ethanone-1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-1-(O-acetyloxime),[4-(methylphenylthio)phenyl]phenylmethanone, and oligo{2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone}.

Specific examples of the hydrogen-abstracting polymerization initiatorinclude, but are not limited to, benzophenone compounds such asbenzophenone, methylbenzophenone, methyl-2-benzoylbenzoate,4-benzoyl-4′-methyldiphenyl sulfide and phenylbenzophenone; andthioxanthone compounds such as 2,4-diethylthioxanthone,2-chlorothioxanthone, isopropylthioxanthone and1-chloro-4-propylthioxanthone.

Amines can be used together as a polymerization accelerator.

Specific examples thereof include, but are not limited to,p-dimethylaminobenzoate, 2-ethylhexyl p-dimethylaminobenzoate, methylp-dimethylaminobenzoate, 2-dimethylaminoethyl benzoate and butoxyethylp-dimethylaminobenzoate.

The photopolymerizable composition may be transparent without includinga colorant, and may include a colorant when necessary. When thephotopolymerizable composition is desired to be colorless or white,materials having less color are preferably used besides thepolymerization initiator, the polymerization accelerator and thecolorant.

Known inorganic pigments and organic pigments can be used as a colorantcoloring the photopolymerizable composition.

Specific examples of black pigments include, but are not limited to,carbon black produced by a furnace method of a channel method.

Specific examples of yellow pigments include, but are not limited to,pigments of Pigment Yellow series, such as Pigment Yellow 1, PigmentYellow 2, Pigment Yellow 3, Pigment Yellow 12, Pigment Yellow 13,Pigment Yellow 14, Pigment Yellow 16, Pigment Yellow 17, Pigment Yellow73, Pigment Yellow 74, Pigment Yellow 75, Pigment Yellow 83, PigmentYellow 93, Pigment Yellow 95, Pigment Yellow 97, Pigment Yellow 98,Pigment Yellow 114, Pigment Yellow 120, Pigment Yellow 128, PigmentYellow 129, Pigment Yellow 138, Pigment Yellow 150, Pigment Yellow 151,Pigment Yellow 154, Pigment Yellow 155, and Pigment Yellow 180.

Specific examples of magenta pigments include, but are not limited to,pigments of Pigment Red series, such as Pigment Red 5, Pigment Red 7,Pigment Red 12, Pigment Red 48(Ca), Pigment Red 48(Mn), Pigment Red57(Ca), Pigment Red 57:1, Pigment Red 112, Pigment Red 122, Pigment Red123, Pigment Red 168, Pigment Red 184, Pigment Red 202, and PigmentViolet 19.

Specific examples of cyan pigments include, but are not limited to,pigments of Pigment Blue series, such as Pigment Blue 1, Pigment Blue 2,Pigment Blue 3, Pigment Blue 15, Pigment Blue 15:3, Pigment Blue 15:4,Pigment Blue 16, Pigment Blue 22, Pigment Blue 60, Vat Blue 4, and VatBlue 60.

Specific examples of white pigments include, but are not limited to,sulfuric acid salts of alkaline earth metals such as barium sulfate;carbonic acid salts of alkaline earth metals such as calcium carbonate;silica such as fine silicic acid powder and synthetic silicic acidsalts; calcium silicate; alumina; alumina hydrate; titanium oxide; zincoxide; talc; and clay.

In addition, various inorganic or organic pigments may be optionallyused considering, for example, physical properties of thephotopolymerizable composition.

Further, in the photopolymerizable composition, a polymerizationinhibitor (e.g., 4-methoxy-1-naphthol, methylhydroquinone, hydroquinone,t-butylhydroquinone, di-t-butylhydroquinone, methoquinone,2,2′-dihydroxy-3,3′-di(α-methylcyclohexyl)-5,5′-dimethyldiphenylmethane,p-benzoquinone, di-t-butyl diphenylamine, and9,10-di-n-butoxyanthracene,4,4′-[1,10-dioxo-1,10-decandiylbis(oxy)]bis[2,2,6,6-tetramethyl]-1-piperidinyloxy),a surfactant (e.g., higher fatty acid ester containing polyether, anamino group, a carboxyl group, or a hydroxyl group, apolydimethylsiloxane compound containing, in its side chain or terminal,polyether, an amino group, a carboxyl group, or a hydroxyl group, and afluoroalkyl compound containing a polyether residue, an amino group, acarboxyl group, and a hydroxyl group), and a polar group-containingpolymer pigment dispersing agent may be optionally used.

The ink of the present invention can be housed in a container, and usedas an ink cartridge. With this form, users do not have to directly touchthe ink during operations, such as exchange of the ink, and thus thereis no concern about staining of their fingers, hands, clothes, etc. Inaddition, it is possible to prevent interfusion of foreign matter suchas dust into the ink.

The container is not particularly limited, and a shape, structure, size,and material thereof can be appropriately selected depending on theintended purpose. As for the container, for example, preferred is acontainer having an ink bag formed of an aluminum laminate film, or aresin film.

The ink cartridge will be explained with reference to FIGS. 1 and 2.FIG. 1 is a schematic diagram illustrating one example of an ink bag 241of the ink cartridge, and FIG. 2 is a schematic diagram illustrating theink cartridge 200, in which the ink bag 241 of FIG. 1 is housed in acartridge case 244.

As illustrated in FIG. 1, the ink bag 241 is filled with the ink byinjecting the ink from an ink inlet 242. After removal of air presentinside the ink bag 241, the ink inlet 242 is sealed by fusion bonding.At the time of use, a needle attached to the main body of the device isinserted into an ink outlet 243 formed of a rubber member to supply theink to the device therethrough. The ink bag 241 is formed of a wrappingmember such as an air non-permeable aluminum laminate film. Asillustrated in FIG. 2, the ink bag 241 is typically housed in a plasticcartridge case 244, which is then detachably mounted in various inkjetrecording devices to thereby use as the ink cartridge 200.

The ink cartridge of the present invention is preferably detachablymounted in inkjet recording devices. The ink cartridge can simplify therefill and exchange of the ink to improve workability.

As for a coating base for the ink of the present invention, paper,plastic, metal, ceramic, glass, or a composite material thereof is used.Since a permeable base, such as wood free paper, can expect an effect ofpenetrating and drying, it is practical to use an aqueous ink or an oilink, which is not a quick-drying ink, for such base. On the other hand,it is practical to use a quick-drying ink for a hard-permeation or anon-permeable base, such as gloss coat paper, a plastic film, a plasticmolded article, ceramic, glass, metal, and rubber.

The ink of the present invention is preferably used on, but is notlimited to, the surface of metals because of having good adherencethereto. In addition, the ink is preferably used on the non-permeablebase as well because of being immediately cured upon application oflight. Among the non-permeable bases, the ink of the present inventionis suitably used for a plastic material, such as a plastic film, and aplastic molded article, which is formed of polyethylene, polypropylene,polyethylene terephthalate, polycarbonate, an ABS resin, polyvinylchloride, polystyrene, any of other polyesters, polyamide, a vinyl-basedmaterial, or a composite material thereof.

EXAMPLES

Having generally described this invention, further understanding can beobtained by reference to certain specific examples which are providedherein for the purpose of illustration only and are not intended to belimiting. In the descriptions in the following examples, the numbersrepresent weight ratios in parts, unless otherwise specified.

<Evaluation Method of SI Value>

According to the skin sensitization test based on the LLNA (Local LymphNode Assay), the SI value was measured in the manner described below.

[Test Material]

<<Positive Control>>

α-hexylcinnamaldehyde (HCA; product of Wako Pure Chemical Industries,Ltd.) was used as the positive control.

<<Medium>>

As a medium, a mixture containing acetone (product of Wako Pure ChemicalIndustries, Ltd.) and olive oil (product of Fudimi Pharmaceutical Co.,Ltd.) in a volume ratio of 4/1 was used.

<<Animals Used>>

Before treated with the test substances, the positive control or themedium control, female mice were acclimated for 8 days including 6-dayquarantine. No abnormalities were found in all the mice (used animals)during the quarantine/acclimation period.

Based on the body weights measured 2 days before the initiation ofsensitization, they were categorized into 2 groups (4 mice/group) by thebody weight stratified random sampling method so that the body weight ofeach individual was within ±20% of the average body weight of all theindividuals. Each of the used animals was 8 weeks old to 9 weeks old atthe time of the initiation of sensitization. The individuals remainingafter the categorization were excluded from the test.

The used animals were individually identified by application of oil inkto their tale throughout the test period, and also their cages werelabeled for identification.

<<Housing Environment>>

Throughout the housing period including the quarantine/acclimationperiod, the used animals were housed in an animal room with barriersystem, which was set as follows: 21° C. to 25° C. in temperature, 40%to 70% in relative humidity, 10 times/hour to 15 times/hour in frequencyof air circulation, and a 12 hour-interval lighting cycle (lighting from7:00 to 19:00).

The housing cages used were those made of polycarbonate, and fouranimals were housed in each cage.

The used animals were given ad libitum solid feed for laboratory animalsMF (product of Oriental Yeast Co., Ltd.). Also, using a water-supplybottle, the used animals were given ad libitum tap water in which sodiumhypochlorite (PURELOX, product of OYALOX Co., Ltd.) had been added sothat the chlorine concentration was about 5 ppm. Bedding used wasSUNFLAKE (fir tree, shavings obtained with a power planer) (product ofCharles River Inc.). The feed and all of the feeding equipments weresterilized with an autoclave (121° C., 30 min) before use.

The housing cage and the bedding were replaced with new ones at thetimes of the categorization and the removal of the auricular lymph node(i.e., the time when the animals were transferred from the animal room),and the water-supply bottle and rack were replaced with new ones at thetime of the categorization.

[Test Method]

<<Group Composition>>

The group compositions of the medium control group and positive controlgroup used for the measurement of the Si value are shown in Table 1.

TABLE 1 Sensitization Number of Sensitization dose Times of animals Testgroup substance (μL/auricle) sensitization (animal No.) Medium Medium 25Once/day × 4 control group only 3 days (1-4) Positive 25.0% HCA 25Once/day × 4 control group 3 days (5-8)[Preparation]<<Test Substance>>

Table 2 shows the amount of the test substance. The test substance wasweighed in a measuring flask, and the volume of the test substance wasadjusted to 1 mL with the medium. The thus-prepared test substancepreparation was placed in a light-shielded airtight container (made ofglass).

TABLE 2 Concentration after adjustment Mass of test (w/v %) substance(g) Test 50.0 0.5 substance<<Positive Control Substance>>

About 0.25 g of HCA was accurately weighed, and the medium was added tothe HCA to have the volume of 1 mL, to thereby prepare a 25.0% by masssolution. The thus-prepared positive control substance preparation wasplaced in a light-shielded airtight container (made of glass).

<<BrdU>>

In a measuring flask, 200 mg of 5-bromo-2′-deoxyuridine (BrdU, productof NACALAI TESQUE, INC.) was accurately weighed in a measuring flask.Then, physiological saline (product of OTSUKA PHARMACEUTICAL CO., LTD.)was added to the measuring flask, and dissolved through application ofultrasonic waves. Thereafter, the volume of the resultant solution wasadjusted to 20 mL to prepare a 10 mg/mL solution (BrdU preparation). TheBrdU preparation was sterilized through filtration with a sterilizedfiltration filter and placed in a sterilized container.

<<Preparation Day and Storage Period>>

The positive control preparation was prepared on the day before theinitiation of sensitization, and stored in a cold place except in use.The medium and the test substance preparations were prepared on the dayof sensitization. The BrdU preparation was prepared 2 days beforeadministration and stored in a cold place until the day ofadministration.

[Sensitization and Administration of BrdU]

<<Sensitization>>

Each (25 μL) of the test substance preparations, the positive controlpreparation or the medium was applied to both the auricles of each ofthe used animals using a micropipetter. This treatment was performedonce a day for three consecutive days.

<<Administration of BrdU>>

About 48 hours after the final sensitization, the BrdU preparation (0.5mL) was intraperitoneally administered once to each of the used animals.

[Observation and Examination]

<<General Conditions>>

All the used animals used for the test were observed once or more timesa day from the day of the initiation of sensitization to the day of theremoval of the auricular lymph node (i.e., the day when the animals weretransferred from the animal room). Notably, the observation day wascounted from the day of the initiation of sensitization being regardedas Day 1.

<<Measurement of Body Weights>>

The body weight of each of the used animals was measured on the day ofthe initiation of sensitization and on the day of the removal of theauricular lymph node (i.e., the day when the animals were transferredfrom the animal room). Also, the average of the body weights and thestandard error thereof were calculated for each group.

<<Removal of Auricular Lymph Node and Measurement of Weight Thereof>>

About 24 hours after the administration of BrdU, the used animals wereallowed to undergo euthanasia, and their auricular lymph nodes weresampled. The surrounding tissue of each auricular lymph node wasremoved, and the auricular lymph nodes from both the auricles werecollectively weighed. Also, the average of the weights of the auricularlymph nodes and the standard error thereof were calculated for eachgroup. After the measurement of the weights, the auricular lymph nodesof each individual were stored in a frozen state using a BIO MEDICALFREEZER set to −20° C.

<<Measurement of BrdU Intake>>

After returning the auricular lymph nodes to room temperature, theauricular lymph nodes were mashed with the gradual addition ofphysiological saline, and suspended therein. The thus-obtainedsuspension was filtrated and then dispensed into the wells of a 96-wellmicroplate, with 3 wells being used per individual. The thus-dispensedsuspensions were measured for intake of BrdU by the ELISA method. Thereagents used were those of a commercially available kit (CellProliferation ELISA, BrdU colorimetric, Cat. No. 1647229, product ofRoche Diagnostics Inc.). A multiplate reader (FLUOSTAR OPTIMA, productof BMG LABTECH Inc.) was used to measure the absorbance of each well(OD: 370 nm to 492 nm, the intake of BrdU), and the average of theabsorbance of the 3 wells for each individual was used as themeasurement of BrdU for the individual.

[Evaluation of Results]

<<Calculation of Stimulation Index (SI)>>

As shown in the following formula, the measurement of BrdU intake foreach individual was divided by the average of the measurements of BrdUintake in the vehicle control group to calculate the SI value for theindividual. The SI value of each test group was the average of the SIvalues of the individuals. Also, the standard error of the SI values wascalculated for each test group. Notably, the SI value was rounded at thesecond decimal place and shown to the first decimal place.

${SI} = \frac{\begin{matrix}{{{Averageof}\mspace{14mu}{measurements}\mspace{14mu}{of}\mspace{14mu}{BrdU}\mspace{14mu}{intake}}\mspace{14mu}} \\{{for}\mspace{14mu}{each}\mspace{14mu}{individual}\;( {{average}\mspace{14mu}{of}\mspace{14mu} 3\mspace{14mu}{wells}} )}\end{matrix}}{\begin{matrix}{{{Averageof}\mspace{14mu}{measurements}\mspace{14mu}{of}\mspace{14mu}{BrdU}\mspace{14mu}{intake}\mspace{14mu}{in}\mspace{14mu}{the}}\mspace{14mu}} \\{{vehicle}\mspace{14mu}{control}\mspace{14mu}{group}\;( {{average}\mspace{14mu}{of}\mspace{14mu} 4\mspace{14mu}{animals}} )}\end{matrix}}$

Examples 1 to 12 and Comparative Examples 1 to 3

The following materials (a), (b) and (c) were mixed at ratios (parts byweight) shown in Tables 3-1 to 3-4 to prepare inks of Examples andComparative Examples.

(a) (Meth)acrylic acid ester having negative skin sensitization

(b) Methacrylic acid ester having a phosphoric group

(c) Photopolymerization initiator

TABLE 3-1 Com. Material Ex. 1 Ex. 1 Ex. 2 Ex. 3 a a1 95 80 80 80 a2 5 55 5 a3 b b1 15 b2 15 b3 15 c c1 20 20 20 20 Viscosity (mPa · s) 25° C. 716 19 15 45° C. *1 8 9 8 60° C. *1 *1 *1 *1 Ejection Head Temperature25° C. 45° C. 45° C. 45° C. in Inkjet Printing Adherence Inkjet Aluminum5 0 0 1 Printing Stainless 5 0 0 0 Brush Aluminum 5 0 0 0 coatingStainless 5 0 0 1

TABLE 3-2 Com. Material Ex. 2 Ex. 4 Ex. 5 Ex. 6 a a1 50 45 45 45 a2 a350 45 45 45 b b1 10 b2 10 b3 10 c c1 20 20 20 20 Viscosity (mPa · s) 25°C. 16 24 30 22 45° C. 8 10 13 9 60° C. *1 *1 *1 *1 Ejection HeadTemperature 45° C. 45° C. 45° C. 45° C. in Inkjet Printing AdherenceInkjet Aluminum 5 0 0 0 Printing Stainless 5 0 0 1 Brush Aluminum 5 0 00 coating Stainless 5 0 0 0

TABLE 3-3 Com. Material Ex. 3 Ex. 7 Ex. 8 Ex. 9 a a1 70 60 60 60 a2 1010 10 10 a3 20 20 20 20 b b1 10 b2 10 b3 10 c c1 15 15 15 15 Viscosity(mPa · s) 25° C. 14 27 31 26 45° C. 8 11 13 10 60° C. *1 *1 *1 *1Ejection Head Temperature 45° C. 45° C. 45° C. 45° C. in Inkjet PrintingAdherence Inkjet Aluminum 5 0 0 0 Printing Stainless 5 0 0 0 BrushAluminum 5 0 0 1 coating Stainless 5 0 0 0

TABLE 3-4 Material Ex. 10 Ex. 11 Ex. 12 a a1 70 70 70 a2 a3 b b1 30 b230 b3 30 c c1 20 20 20 Viscosity (mPa · s) 25° C. 32 36 31 45° C. 15 1814 60° C. *1 8 *1 Ejection Head Temperature in Inkjet Printing 45° C.60° C. 45° C. Adherence Inkjet Aluminum 0 0 0 Printing Stainless 0 0 1Brush Aluminum 0 0 1 coating Stainless 0 0 0*1: Viscosity was not measured because the ink was ejectable at lowertemperature.

Details of a1 to a8 and b1 are as follows. Values in ( ) at the ends areSI values in (1) LLNA test, and “None” means “negative for skinsensitization” or “no skin sensitization” in (2) MSDS (Material SafetyData Sheet).

-   (a) (Meth)acrylic acid ester having negative skin sensitization (a1    to a3)-   a1: diethyleneglycol dimethacrylate (n=2) “2G” from Shin-Nakamura    Chemical Co., Ltd., (1.1)-   a2: caprolactone-modified dipentaerythritol hexaacrylate DPCA 60    from Nippon Kayaku Co., Ltd. (Negative in MSDS)-   a3: ethyleneoxide-modified trimethylolpropanetrimethacrylate (n=3)    “TMPT-3EO” from Shin-Nakamura Chemical Co., Ltd., (1.0)-   (b) Methacrylic acid ester having a phosphoric group (b1 to b3)-   b1: Methacrylic acid ester including a phosphoric group having a    formula (CH₂═C(CH₃)COOCH₂CH₂O)₂—P(═O)OH “LIGHT ESTER P-2M” from    Kyoeisha Chemical Co. LTD.-   b2: Methacrylic acid ester including a phosphoric group having a    formula (CH₂═C(CH₃)COOCH₂CH₂O—P(═O)(—OH)₂ “LIGHT ESTER P-1M” from    Kyoeisha Chemical Co. LTD.-   b3: Methacrylic acid ester including a phosphoric group having a    formula (CH₂═C(CH₃)COOCH₂CH₂OCO(CH₂)₅O)₂—P(═O)OII “KAYAMER PM21”    from NIPPON KAYAKU Co., Ltd.-   (c) Photopolymerization initiator (c1)-   c1: 1-hydroxycyclohexylphenylketone “Irgacure 184” from BASF    (Negative in MSDS)

The viscosity (mPa·s) and the strength of coating film at 25, 45 and 60°C. of each ink were measured.

The viscosity of each ink was measured by a cone plate-type rotaryviscometer (manufactured by TOKI SANGYO CO., LTD.) with the temperatureof circulating water being constantly set 25, 45 and 60° C. Thetemperature of 25° C. is temperature set considering typical roomtemperature. The temperatures of 45 and 60° C. are temperatures of aheatable marketed inkjet ejection head such as GEN4 from Ricoh PrintingSystems, Ltd.

The photopolymerizable composition prepared at a predeterminedcombination was used as it was in evaluation by brush coating. Toevaluate inkjet ink, after the ink was filtered through a membranefilter made of fluorine resin, having a pore diameter of 5 microns, theink was sealed in an aluminum pouch bag having the shape in FIG. 1 sothat a bubble was formed. The pouch bag the ink was sealed in wascontained in a plastic cartridge as shown in FIG. 2. In a chassiscapable of containing the cartridge, an ink flow channel was formed fromthe cartridge to the GEN4 head from Ricoh Printing Systems, Ltd. toeject the ink and form a solid coating film. Each of the brush coatingand the inkjet printing was controlled to form a solid coating filmhaving a thickness about 40 microns.

A solid coating film formed on a marketed aluminum-laminatedpolyethyleneterephthalate film (ALPET 9-100 having a thickness of 100microns from PANAC Corp.) and a solid coating film formed on a generaluse stainless plate (SUS304 having a thickness of 0.5 mm) wereirradiated at 0.3 W/cm² and 1.2 J/cm² and hardened so as to evaluateadherence and strength thereof.

Scratch hardness of the irradiated and hardened coating film wasevaluated by a pencil method specified in JIS-K-5600-5-4. Pencilhardness includes 2H, H, F, HB, B, 2B to 6B in descending order ofhardness.

The adherence of the solid coating film hardened by irradiation wasevaluated by a crosscut method specified in JIS-K-5600-5-6. Tape peelingtest was performed on tessellated 25 squares formed at an interval of 1mm to visually observe the remaining squares and classify them into 6ranks (0 to 5). Zero (0) means no peeling of the square and goodadherence. The larger, the worse. The details are omitted because ofbeing disclosed in JIS-K-5600-5-6.

The evaluation results are shown in Tables 3-1 to 3-4 and 4-1 to 4-3.

TABLE 4-1 Material Ex. 1 Ex. 2 Ex. 3 Ex. 4 a a1 80 80 80 45 a2 5 5 5 a345 b b1 15 10 b2 15 b3 15 c c1 20 20 20 20 Coating Inkjet B 2B 3B HBFilm Printing Strength Brush B 2B 3B HB Coating

TABLE 4-2 Material Ex. 5 Ex. 6 Ex. 7 Ex. 8 a a1 45 45 60 60 a2 10 10 a345 45 20 20 b b1 10 b2 10 10 b3 10 c c1 20 20 15 15 Coating Inkjet B 2BF HB Film Printing Strength Brush B 2B F HB Coating

TABLE 4-3 Material Ex. 9 Ex. 10 Ex. 11 Ex. 12 a a1 60 70 70 70 a2 10 a320 b b1 30 b2 30 b3 10 30 c c1 15 20 20 20 Coating Inkjet 2B 2B 6B 6BFilm Printing Strength Brush 2B 2B 6B 6B Coating

As Tables 3-1 to 3-4 show, (b) methacrylic acid ester having aphosphoric group improves adherence to metal surfaces. Particularly, themethacrylic acid esters having a phosphoric group b1 having the formula(CH₂═C(CH₃)COOCH₂CH₂O)₂—P(═O)OH or b2 having the formulaCH₂═C(CH₃)COOCH₂CH₂O—P(═O)(—OH)₂ more improve the adherence.

Further, methacrylic acid ester having a phosphoric group b1 having theformula (CH₂═C(CH₃)COOCH₂CH₂O)₂—P(═O)OH particularly improves strengthof the coating film.

There were no noticeable differences between coating films formed by theinkjet printing and the brush coating. All the photopolymerizablecompositions and the inks had no particular odors to be cautioned.

Having now fully described the invention, it will be apparent to one ofordinary skill in the art that many changes and modifications can bemade thereto without departing from the spirit and scope of theinvention as set forth therein.

What is claimed is:
 1. A photopolymerizable composition, comprising:diethyleneglycol dmethacrylate; methacrylic acid ester having aphosphoric group; and caprolactone-modified dipentaerythritolhexaacrylate.
 2. The photopolymerizable composition of claim 1, whereinthe methacrylic acid ester having a phosphoric group comprises astructure having a formula:(CH₂═C(CH₃)COOCH₂CH₂O)₂—P(═O)OH.
 3. The photopolymerizable compositionof claim 1, further comprising ethyleneoxide-modified trimethylolpropanetrimethacrylate.
 4. An inkjet ink, comprising the photopolymerizablecomposition according to claim
 1. 5. A cartridge, comprising the inkjetink according to claim
 4. 6. A coated matter coated with thephotopolymerizable composition according to claim
 1. 7. Thephotopolymerizable composition of claim 1, wherein an amount of themethacrylic acid ester having a phosphoric group in thephotopolymerizable composition is from 5 to 30 parts by weight per 100parts by weight of monomer components.
 8. The photopolymerizablecomposition of claim 1, wherein an amount of the diethyleneglycoldimethacrylate in the photopolymerizable composition is from 45 to 80parts by weight per 100 parts by weight of monomer components.
 9. Thephotopolymerizable composition of claim 1, wherein an amount of thecaprolactone-modified dipentaerythritol hexaacrylate in thephotopolymerizable composition is from 5 to 10 parts by weight per 100parts by weight of monomer components.
 10. The photopolymerizablecomposition of claim 1, wherein the amount of the methacrylic acid esterhaving a phosphoric group in the photopolymerizable composition is from5 to 30 parts by weight per 100 parts by weight of monomer components,the amount of the diethyleneglycol dimethacrylate in thephotopolymerizable composition is from 45 to 80 parts by weight per 100parts by weight of monomer components, and the amount of thecaprolactone-modified dipentaerythritol hexaacrylate in thephotopolymerizable composition is from 5 to 10 parts by weight per 100parts by weight of monomer components.
 11. The photopolymerizablecomposition of claim 1, wherein the methacrylic acid ester having aphosphoric group comprises a structure having a formula:CH₂═C(CH₃)COOCH₂CH₂O—P(═O)(—OH)₂.
 12. The photopolymerizable compositionof claim 1, further comprising a photoradical polymerization initiator.